1. Field of the Invention
This invention is an improvement to the invention set forth in my U.S. Pat. No. 4,677,963, issued Jul. 7, 1987, and the teachings and technology thereof are incorporated herein by reference. The invention herein relates to the cutting art and, more particularly, to an improved annular cutting disc.
2. Description of the Prior Art
In many applications, an annular cutting disc is utilized as a cutting tool. In such applications, the disc is generally a flat, comparatively thin, metallic core member which has an outer wall having attachment means for attachment to a rotary motion producing device. The disc has an inner annular wall and the inner annular wall, provided with appropriate coatings on the core member, defines the cutting edge.
With the increased activities in the semi-conductor field, wherein crystals of comparatively high unit cost must be precisely cut, such annular cutting discs have been utilized. In order to provide the cutting edge, the prior art annular cutting discs had a coating of a slurry of a nickel matrix with diamond particles or bits therein plated on the core member to provide the actual cutting edge. The diamond particles in the nickel matrix were generally in the range of, for example, 30 to 80 microns in size.
Materials associated with the semi-conductor industry, such as gallium arsenide, silicon, and the like, are comparatively high cost. Consequently, it is desired to minimize the amount of waste material made during the cut of such structures. It is, therefore, desired to make as thin a cut as possible. Additionally, it is necessary that the edges of the material being cut be as planar and free from surface irregularities as possible, because of the precision required in such structures after they are cut.
While the above-described general configuration of an annular cutting disc has, at times, provided a satisfactory cutting of such materials as gallium arsenide, or silicon, or the like, as utilized in the semi-conductor industry, in general, it has been found that when the core member is made thinner in order to minimize the loss of the material being cut, precision of the cut was not maintained, due to wobble and/or bowing of the core member during the cutting operation. The bowing or wobbling of the blade not only caused excessive waste during the cut, but also, depending upon the exact motion of the blade, could cause convex or concave edges to the material being cut, which could cause decreased performance capability and/or require discarding of the cut material
Also, as described in my U.S. Pat. No. 4,677,963, loosely held diamond particles tended to either break loose or to cause an uneven or "ridged" cut in the material being cut, and such cuts or ridges could be in the range of 30 microns deep. Such ridges or cuts tended to degrade the performance of the gallium arsenide, silicon, or the like, when it was ultimately utilized in various semi-conductor devices.
Prior art annular cutting discs of the type shown, for example, in U.S. Pat. Nos. 3,205,624 or 3,626,921 did not recognize the problem solved by my invention in U.S. Pat. No. 4,677,963 of removing the loosely held diamond particles or bits from the surfaces of the slurry coating.
In my above-identified U.S. Pat. No. 4,677,963, I have taught how an annular cutting disc may be fabricated to eliminate the bowing or wobbling of the blade and, also, to eliminate the "uneven" or "ridged" cut in the material being cut caused by loose diamond particles or bits. However, it has now been found that even greater accuracy in the cutting of the semi-conductor materials such as gallium arsenide, silicon, or the like, with even less materials wasted during the cut and/or less unsatisfactory materials is desired.
It has been found that one of the causes of damage or irregular cut edges in the material being cut is a thermal effect caused by overheating of the annular cutting disc and/or the material being cut. The thermal effects caused by overheating can be wobble or bowing of the annular cutting disc, and other effects which increase the material wasted during the cutting operation and/or provide improperly cut surfaces. In order to reduce these deleterious thermal effects, it is necessary to provide coolant impinging on the cutting disc as close as possible to the source of the heat generation. This source of heat generation is located at the cutting interface comprising the contact area of the annular cutting disc and the material being cut. Primarily, as noted above, it is the inner edge of the diamond slurry coating on the core member which provides the cutting action. However, the radial sides of the diamond slurry may also contact the material being cut because of vibration, slight disc misalignment, wear on the blade, and the like. Therefore, it has long been desired to provide an arrangement in which a coolant may be provided closer to the cutting interface to thereby maintain a lower temperature of the disc and material being cut in order to minimize the thermal effects.
It will be appreciated that, during the cutting operation, the material being cut is, of course, in contact with or very closely adjacent to the cutting surfaces such as the cutting edge, which prevents the application of coolant directly at the location of cutting.
Therefore, coolant is generally applied in directions radially inwardly toward the cutting interface along the annular cutting disc to remove heat from the cutting disc and the material being cut.
Accordingly, there has long been a need for an annular cutting disc which will provide even greater accuracy with less waste desired in the fabrication of the semiconductor materials by minimizing deleterious thermal effects occurring during the cutting operation. However, the present invention is not limited to an annular cutting disc for such material: rather, it can be advantageously utilized in a plurality of applications.